Heat exchange system



- 1949 E. P. HARRISON ET AL 2,490,266

HEAT EXCHANGE SY STEM v 4 Shets-Sheet 1 Original Filed March 15, 1944 INVEN TORSI ElmerPa 111 H an'ison andaruille H. Huni Arr'Ys.

Dec. 6, 1949 Original Filed March 15, 1944 E. P. HARRISON EI'AL 2,490,266

HEAT EXCHANGE SYSTEM 4 Sheets-Sheet 2 49 /42 I48 'dMZ INVENTORS: ElmerPaulHarrison andflwille flJIuni ATTYs.

Dec. 6, 1949 E. P. HARRISON ETAL 2,490,266

HEAT EXCHANGE SYSTEM Original Filed March 13, 1944 4 Sheets-Sheet 3 INVENTORS: ElmrPau/Hmvisan 21nd0rvil/e4 lizmi Dec. 6, 1949 E. P. HARRISON ETAL 2,490,266

HEAT EXCHANGE SYSTEM Original Filed March 13, 1944 I 4 Sheets-Sheet 4 v INVENTORSJ ElmerPaulHawison I]? 16 Q andOrvilIeAHzmf M fiM Patented Dec. 6, 1949 HEAT EXCHANGE SYSTEM Elmer Paul Harrison, Chicago, Ill., and Orville A. Hunt, Oklahoma City, Okla., assignors, by direct and mesne assignments, to Reconstruction Finance Corporation, Chicago, 111., a corporation of the United States Original application March 13, 1944, Serial No. 526,152. Divided and this application March 8, 1945, Serial N0. 581,586

. 14 Claims.

The present application is a division of our co-pending application, entitled Heat exchange system, Serial No. 526,152, filed March 13, 1944, now abandoned.

This invention relates to a steam system employing steam substantially above atmospheric pressure as distinguished from a vacuum system for heat processing material, and using steam of a quality such that the major portion of the heat to be used for heat processing must be derived from the latent heat of steam rather than its sensible heat. More particularly, the invention relates to a heat exchange system in which the heat from live steam is transferred through the walls of steam chests, and the heated wall surfaces are used for drying wet clothing, wet paper rolls, and the like, in laundries, factories, mills and like places, as Well as to a particular method of handling and utilizing the steam in such systems. clarity the invention has been illustrated for use in connection with a laundry plant, although it may be used in paper plants and the like.

A primary object is to provide means for raising the production level or actual heat output of steam plants with special reference to plants for processing traveling sheet material as in the laundry and paper manufacturing fields. Heretofore such plants have been operated year after year at what the present invention reveals as unnecessarily low rates of heat output. In other words, the present invention enters levels of heat output substantially above the heretofore commonly accepted limit for given systems and for conventional apparatus.

In the drying of a given sheet material with a given initial moisture content, the heat output varies directly as the product of the feet per minute travel and the temperature rise of the material. accepted heat output limit of a four-roll ironer is represented by the commonly accepted speed of the ironer in feet per minute for given fiat work. To run a four-roll ironer in a conventional steam system at substantially higher than the For purposes of Thus, for example, the commonly Our invention is based on two discoveries, the first discovery being that raising the velocity of steam flow through the system will move condensate and air out of the system so effectively as to make traps unnecessary, and, second, the discovery of how such increased velocities of flow may be achieved economically by releasing steam from the system. Heretofore, the desirability of the higher rates of steam flow Within the heat-transferring apparatus has not been fully appreciated, traps that preclude such rates of flow have been commonly regarded as necessary for condensate disposal and the problem of economically achieving such flow of velocities by releasing steam from the system has not been solved.

The heretofore usual rates of steam fiow in conventional steam systems have permitted relatively heavy films of condensate to blanket the heat transfer walls to such extent as to limit the rate of heat transfer from the flowing steam to the exterior surfaces of the heat transfer walls.

Our purpose is achieved by releasing steam from the return side of the system substantially continuously or by releasing steam in a suitably intermittent manner and preferably by making the heat demand presented to the system a factor for automatic regulation of either continuous or intermittent steam release. Many practices of our invention are characterized by a, pulsating flow of steam through the system. The mode of operation may be termed pulsating continuous flow of steam in those instances in which the variation in each impulse is between two different positive rates of flow or may be termed pulsating intermittent flow of steam in those instances in which the variation in each impulse reach zero velocity. In any mode of operation, however, the average steam velocity over a period of time or the number of occurrences of flow at effective velocity over the period of time is so effective in removing condensate and non-condensable gases from the system as to bring the heat output into the new higher levels.

If the steam is released substantially continuously, the minimum rate for low heat demand will be adequate but not exorbitant and the rate will increase with demand. In some installations, the higher rates of steam release would be exorbitant, even prohibitive, if constantly maintained but become economically justified when occurring only concurrently with increased demand for heat from the system by the traveling sheet material.

With respect to intermittent release of steam termittency in accord with the demand for heat lo by the sheet material. In some practices of our invention, a demand for heat exterior to the system such as a demand for hot water for outside use is one of the factors determining the rate at which steam is released from the system, but in such practices, it is contemplated that in the absence of such outside demand, the remaining factors including the demand for heat by the material in process will be suflicient to maintain the internal steam velocity at a sufficiently high rate to bring the heat output into the new higher range of levels.

Some of the important concepts that may be found singly or in combination in various practices or our invention include: releasing steam in a pulsating intermittent manner by employing a steam valve that will completely cut on when a thermostat is heated to a predetermined temperature; employing the feed Water supply as means for causing the rate of steam release to vary in ually released from the system regardless of demand, i. e., to insure inherently a sufficiently high rate of steam release to enter the new range of heat output; to insure the required high range of flow velocity by releasing steam both in response to the feeding of water to the steam generator and in response to the requirement for steam release to meet the tendency of a thermostat to cool below a relatively high temperature setting; to release steam in direct response to changes in the temperature of heat exchange walls; to release steam in accord with automatic variation in fuel feed to meet different levels in heat demand by the material in process; to achieve a desirable intermittent action by making a steam system inherently unstable; to set up a chain of causes in a steam system to achieve a desired steam releasing effect; to take advantage of lag factors in a steam system for the purpose of the invention; to combine the release of steam with the deaeration of feed water both in the sense of using released steam for deaeration and in the sense of using deaeration together with high velocity steam flow to minimize the effects of non-condensable gases in the system.

Additional objects of the invention include the following:

To provide a novel and efiicient manner of deaerating feed water and condensate which is delivered to the boiler; to provide a steam flow system which combines with it appropriate means for deaerating not only new make-up water but also condensate return from the system; to use for auxiliary purposes the steam exhausted from the system to maintain the requisite steam flow through the system and to automatically control the application of the exhaust steam for this pur pose; and, to provide a system and apparatus which is adaptable for use with existing steam plants having a wide range of capacity.

The above and other objects and. advantages of our invention will be apparent in the following detailed description taken with the accompanying drawings.

In the drawings, which are to be considered as merely illustrative;

Fig. l is a diagrammatic view in side elevation of a laundry plant employing one form of the invention,

Fig. 2 is a diagrammatic view in section of two tanks shown in the upper portion of Fig. 1,

Fig. 3 is a diagrammatic View with parts in section showing a portion of the system for deaerating feed water.

Fig. 4 is a horizontal section taken as indicated by the line 4-4 of Fig. 3,

Figs. 5 and 6 are diagrammatic fragmentary views indicating how means may be incorporated in a steam system for different modes of control in response to demand,

Fig. 7 is a section taken as indicated by line 1-1 of Fig- 6,

Fig. 8 is a diagrammatic view of a steam syster incorporating another mode of control in response to demand,

Fig. 9 is a Wiring diagram indicating how an electrically heated thermal means may be employed for controlling intermittent release of steam,

Fig. 10 is a diagrammatic view showing an electrical-mechanical control arrangement for intermittentrelease of steam,

Fig. 11 shows the arrangement of Fig. 10 modified for a difierent mode Of control in response to demand,

Fig. 12 is a Wiring diagram of a control arrangement incorporating an electrical timer,

Fig. 13 is a diagrammatic view indicating how the arrangement in Fig. 12 may be modified for a particular mode of control in response to demand,

Fig. 14 is a diagrammatic view of an arrangement for varying the periods of intermittent steam release in response to demand without varying the frequency of the periods,

Fig. 15 is a wiring diagram of a simple arrangement for providing intermittent steam release, and

Fig. 16 is a wiring diagram of an arrangement for obtaining delayed steam release of adjustable duration.

General description The steam system for a laundry shown by way of example in Figs. 1 to 4 includes the following: a steam generator or boiler 20; means to provide a supply of feed water including a water softener 2 l, two upper tanks 22 and 23, and a lower tank 25; a high pressure steam pipe 26 fed by the boiler; branch pipes 2! with individual valves 28 for delivering the steam to various steamconsuming devices; a main return pipe 30 on the low pressure side of the system; branch pipes 34 equipped with individual valves 32 connecting the various steam-consuming devices or heat exchangers to the main return pipe; and an upright steam pipe 33 connecting the main return pipe 30 with the feed water supply. Tank 22 containing one portion'of the feed water supply may be termed a, soft water storage plant; tank 23 containing another portion may be termed a make-up water tank; and tank 25 al a-"2a containing a third portion may be termed a boiler feed water heater tank. The return side of the pipe system near the lower end of the pipe 33 may be provided with a steam trap 35 and a pipe 36 for conducting condensate from the steam trap to the feed water supply. In Fig. 1 the con densate pipe 36 is shown connected to the previously-mentioned lower tank 25. The system is operated at above atmospheric pressure and back pressure is maintained in the return pipes 38 and 33.

By way of example, the various steam-consuming devices in the above-described, system are indicated as a dry tumbler 31, a flat work ironer 38, a press 48, and a drying form 4!. It is economical in the use of steam to draw on the feed water supply to meet demands for hot water outside of the system. Illustrating such an extraneous demand on the feed water supply, we show in Fig. 1 a pipe 42 for conducting hot water from tank 23 to a washer 43, the pipe being provided with a suitable valve 45.

The feed water arrangement In this first form of the invention, it is contemplated that the steam released primarily for the purpose of achieving effective velocity in the system will be utilized to heat the supply of feed water, that the quantity of the feed water supply, and indirectly the temperature thereof (the latter being affected by the rate at which feed Water is called for by the boiler) will in turn have an important role in the control of velocity by steam release, and that provis on will be made in the feed water arrangement for deaeration of the feed water. The particular feed water arrangement shown in Figs. 1 to 3 is only one of many possible arrangements to provide the contemplated relationships.

The water softener 2! receives its supply from a suitable source through a pipe 46 controlled by a valve 47 and delivers the treated water through a pipe 58. The pipe 48 extends upward to terminate in a discharge valve 58 in the upper tank 22 (Fig. 2), the discharge valve being controlled :by a suitable float 5|. Water from tank 22 may flow to the tank 23 by gravity through a connecting pipe 52 provided with a hand regulating valve 53 and terminating in a discharge valve 55 controlled by a suitable float 55. Water from the softener 2! may also flow through a pipe 5'! branching from the pipe 48 to a heat exchange coil 58 (Fig. 3) associated with the lower tank 25 and may then flow upward through a pipe 68 to a discharge valve 6| controlled by a float 62 in the tank 23.

Steam is released from the steam pipe 33 at the end of the system for the dual purpose of promoting velocity and of preheating the feed water.

The steam pipe 33 extends over and then down into the tank 23 to terminate in a plurality of branch pipes equipped with nozzles 63, each of which nozzles may be an ordinary Penberthy water heater or steam injector. To control the release of steam into the tank 23, the pipe 33 is provided with an electrically-actuated thermally controlled valve 65, the valve being responsive to a thermostat bulb 55 within the tank 23.

Preferably the thermostat bulb 65 is directly above one of the steam nozzles 63 as indicated in Fig. 2 and preferably the thermostat control is highly sensitive to cause valve operation in response to a temperature drop as small as 1 F. The valve of the indicated construction may be or the normally closed type which opens proportionately to provide various rates of flow through the valve in response to a lowering of the water temperature or it may continually bleed a certain amount of steam into the water at all times and open proportionately wider in response to falling temperature of the water. Valves of both types are commercially available and well known and further description is deemed unnecessary. For convenient regulation of steam release a bypass 65 may be provided around valve 65, the bypass being controlled by a bypass valve 69.

A water pipe 61 having a valve 68 for control of flow therethrough leads from the bottom of tank 23 to a downwardly extending jet or injector l8, and steam for operation of the injector is sup plied thereto by a steam pipe H branching from the previously-mentioned steam pipe 33 at the end of the system. Flow of steam through the pipe H is controlled by a suitable steam valve 12 best shown in Fig. 3. The injector 18 is connected to and directed axially into a pipe 13 that leads to a plurality of downwardly directed spray heads or nozzles 15 in the interior of the lower tank 25. Preferably, but not necessarily, both the water valve 68 and the steam valve 12 are snap-acting type valves.

Any suitable electrical or mechanical means may be employed to appropriately control the two valves 58 and 12 as required in the operation of the system. As best shown in Fig. 3, the control means may comprise a lever 16 operated by a float T1 inside the tank 25, the lever having an external arm 18 carrying a pin 88 in engagement with a slot 8| at the lower end of a link 82. The link 82 is operatively connected to both of the valves 68 and T2. The vertical length of the slot 8! should be of minimum dimension to accommo date the snap action of the valves thereby to minimize the drop in liquid level in tank 25 necessary to cause the two valves to open.

The tank 25 is provided with a suitable overflow pipe 83 and below its liquid level connects with a pipe 85 leading to an electrically operated boiler feed pump 86, the feed pump in turn being connected to the boiler 28 by a pipe 8'1. For control of the pump 85, the boiler is provided with an automatic water level control switch 98 which switch preferably is responsive to relatively small differences in liquid level in the boiler.

The provision for deaeration In the above described'system, three different means are employed to heat the feed water in preparation for deaeration in accord with the well known principle that with rising temperature water tends to release any content of permanent gases such as oxygen and air. The three heating means are the heat exchange coil 58, the plurality of steam nozzles 63, and the steam injector 10. In addition to simply raising the temperature of the feed water, we further encourage gas separation by causing at least a substantial portion of the heated water to flash in the lower tank 25. Since the interior of the tank 25 is in communication with the atmosphere through an upper condenser shell 9| surrounding the heat exchange coil 58, it is necessary to bring the water up to certain pressure and temperature values prior to release of the water from the spray nozzles 75. The steam applied to the water through the injector 18 serves to the required extent both to give final heat to the water and to exert pressure on the water. The kinetic energy of the steam introduced through the injector To is transmitted to the water by virtue of the injector being directed in the direction of water flow through the pipe 13, and the spray nozzles 15 sufficiently restrict flow from the pipe 13 to cause the kinetic energy to be transformed into pressure. The interior of the pipe 13 below the injector 19 may aptly be referred to as a pressure zone.

When the water is released from the pressure zone, a portion flashes into steam immediately thereby releasing permanent gases and the remainder of the Water is finely atomized also with release of gases. The released non-condensable gases and the vapor created by the flash action flow upward into the condenser shell 9| where the vapor is largely, if not entirely condensed by contact with the relatively cool coil 58, and the released gases escape to the atmosphere.

Condensate accumulating on the coil 58 trickles downward to a circular condensate tray 92 supported by suitable brackets 93. Preferably the tray is provided with an upstanding concentric collar 95 into which the condensate is directed by a conical skirt 96 at the bottom of the condenser shell, the concentric collar having a serrated lower edge to permit the condensate to flow radially outward along the bottom of the tray. The condensate finally escapes from the tray by dripping over a conical flange 9! around the rim of the tray. This mode of flow by the condensate characterized by thin streams exposed to the upwardly moving vapor and gases effectively in sures that the condensate will be substantially free of permanent gases when it reaches the main body of water in the lower end of the tank 25.

Deaeration is an important factor in attaining efiiciency not only because non-condensable gases, and especially pockets of gases reduce the heat output of heat exchangers, but also because oxygen in feed water is highly detrimental to the system, especially the steam generator. In the practice of our invention, there is an important relationship between deaeration and high velocity flow both in the common purpose of high pro- .ductivity and in the means of accomplishing the purpose. Thus, deaeration removes a large proportion of the non-condensable gases at the boiler feed and the high velocity .of steam flow through the system effectively sweeps away any residual gases surviving the deaeration treatment. In another view of the cooperation between deaeration and high velocity flow, a function of high velocity flow is to continuously scavenge the system of permanent gases and a functionof deaera- :tlOH is to reduce the gas-scavenging task that is left for accomplishment by high velocity flow.

Operation with. substantially continuous steam release In the operation of the described system with substantially continuous release of steam, the thermostat bulb 56 causes the valve 65 to reduce steam flow through'th valve to a minimum or to restrict flow to the bypass 64 whenever the temperature of the water in the tank :23 reaches a predetermined value, a temperature, say, in excess of 160 F.

The setting for minimum flow through the valve 65 or the bypass '66; need not be regarded as critical. The minimum rate of steam released by the valve may in one practice of the invention be sufiicient to cause steam to flow through the whole system with such velocity as to scavenge condensate from the system and to keep all of the heat exchange walls at relatively high temperatures for a high rate of heat output. In another practice, the minimum rate of steam release may be lower so that the periodic release of steam at higher than the minimum rate is required for maintaining efiiciency of operation. In this latter practice, it is necessary only that the temperature of the water in the tank 23 drop often enough to cause sufi'icient flow through the steam valve at higher than the minimum rate. A factor entering into the frequency of operation is the continuous loss of heat from the tank to its environment. The demand by the washer is also a factor that keeps the minimum setting of the thermostat valve from being critical since. the thermostat valve will open for greater than minimum flow whenever any quantity of water is withdrawn from the tank 23 for the washer.

It is apparent that with the liquid level in tank 23 high enough to close both valves and BI, the withdrawal of water from the tank will cause one or both of the discharge valves 55 and BI to open for replenishing flow of relatively cool water. Relatively cool water is supplied by the pipe 68 from the condenser coil 58 and even cooler water is supplied by the pipe 52 from the upper tank 22. If the temperature of the water in tank 23 prior to the lowering of the liquid level therein is sufilciently high at the moment to cause thermostatically controlled valve to operate at minimum fiow, the addition of relatively cool water immediately consequent to the drop in water level will cause the thermostat to open the valve 65 immediately for greater steam release, the higher rate of steam release continuing until normal temperature of the water in the tank 23 is restored after valves 55 and SI close.

A feature of the described. system is the flexibility of operation and the diversity of controls that may be manipulated to vary the character of operation to meet various operating conditions. Among the possible adjustments are: adjustment of the minimum rate of steam flow through the thermostatically controlled valve 65; variation in the temperature setting of the thermostat; adjustment of various valves among valves 28 and 32 in the steam system thereby to control steam flow through the system and/or to set the maximum rate of flow through the steam valve 65; adjustment of the rates of flow through the various float-controlled valves 55 and 6! in tank 23; adjustment of the valve 53 to control the rate of water flow from tank 22 to tank 23; adjustment of the valve 41 to determine the maximum rate at which fresh water may be supplied through the pipe 38; variation in the relative rates of concurrent flow through the water valve 68 and the steam valve 12; and variation in the rate at which the pump 86 transfers water from the tank 25 to the boiler 20. All of these controls should be set to meet particular conditions under which the system operates.

In general, operation of the system with continuous release of steam through the thermostatic valve 65 may be adjusted between the one extreme of steam fiow with minimum variation in rate and the other extreme of steam flow of highly pronounced pulsating character, both extremes of adjustment being based on adequate consideration for the load or heat demand imposed cn the system.

In adjusting the system for minimum variation .in continuous flow, the operator seeks a sumciently high constant rate of steam release to cause sufiiciently high substantially constant velocity through the system for the desired high rate of heat output.

Since the valve 65 responds to changes in the temperature of the water in the tank 23, the operator adjusts the rate of flow of water into the tank in accord with periodic Withdrawal from the tank with a view to maintaining substantially continuous water flow into the tank at a substantially constant rate. In other words, if a given volume of water is withdrawn from the tank at the end of a given time period, the operator seeks a rate of replenishment that will add to the tank content the same quantity over the given period of time. If such an adjustment of replenishing flow is approximated, the steam valve 65 will automatically release steam substantially continuously at a substantially constant rate to bring the continuously added water up to the desired temperature and to compensate for continuous heat losses from the water by radiation. In a laundry having the described arrangement, the washer is will require a new supply periodically through most of the day and will be idle the rest of the day. The operator 'will therefore regulate the flow into the tank 23 at a constant rate equivalent to the feed water demand of the boiler 20 plus the periodic demand of the washer 43. When the washer 43 is shut down, the operator will lower the rate of water delivery to the tank 23 to a level for the rest of the day equivalent to the feed water de mand alone. Regulation of replenishing flow into the tank 23 may be achieved, for example, by adjusting valve 53 and/or other valves in the system as suggested above. The adjustment of replenishing fiow is not to be regarded as highly critical since slightly excessive replenishing flow will merely mean that steam releasedby the valve 65 will be periodically reduced just before periodic delivery of hot water to the washer (i3 and on the other hand somewhat deficient replenishing flow would not be particularly damaging provided it does not permit the tank 23 to run dry.

In adjusting the rate of replenishing flow in the tank 23, the operator, of course, takes into account the load or demand on the system since the feed water demand by the boiler 20 is a function of the load on the system and once the rate of replenishing flow is set, thereafter the thermostatic valve 65 will automatically vary the rate of steam release in accord with any variations in demand that may occur. The automatic response of the thermostatic valve to demand on the system may be readily understood when it is considered that the faster water is withdrawn from tank 23 for boiler feed, the more steam is required to maintain the tank content at the temperature setting of the thermostat. With respect to automatic adjustment of velocity through the system in accord with demand, it

is to be further borne in mind that the more often -the pump 86 operates to replenish the boiler from a factor in the volume of steam release effected in a given system under given operating conditions. If the volume of steam flow at a given thermostat setting is not sufiicient for efiicient operation of the system, the volume may be in- .creased by raising the temperature setting.

If continuous flow of highly pulsating character is desirable in a given installation, the operator provides, by proper valve adjustment, a relatively high rate of replenishing water flow into the tank 23. As a result of such high rate of flow, the liquid level in the tank '23 will be restored in a relatively short time after any withdrawal of hot water for boiler demand or washer demand and the liquid level will thereafter be maintained until the next withdrawal. In fact, the rate'of replenishing flow may be greater than any peak rate of withdrawal so that the liquid level in the tank 23 will remain substantially constant. In either event, the sudden withdrawal of a substantial volume of the tank 23, for example, the volume required to refill the washer 43, will result in a period of relatively high steam flow to restore the temperature in the tank 23 followed by a period of minimum steam flow as determined by the minimum flow adjustment of the valve 65. i

The desirability of pulsating continuous flow under some operating conditions may be readily understood when it is considered that periodic high velocity steam flow tends to flush out the system with more than usual effectiveness, especially peak velocity of flow resulting from relatively wide opening ofthe valve simultaneously with operation of the steam valve 12. The described system inherently favors such periodic simultaneity. Another advantage of pulsating continuous flow is that the lower rate of steam release may not alone be suflicient to sustain a required rate of heat output indefinitely but may sllffioe if assisted by periodic increase in the rate of steam release. In other words, there may be a downward drift in the level of heat output by the system during the periods of rather moderate steam velocity with complete restoration during the recurring periods. of higher steam velocity, the drift being tolerable and more than justified by the resulting saving in fuel cost.

While the described system does have a steam trap 35, it will be notedthatthis trap is in efiect merely a condensate receiver in branch line serv ing as a bypass for delivering some of the condensate direct to the lower tank 25. The system may aptly be termed trapless since the trap 35 does not interfere with the main return flow through pipe 48 and no traps whatsoever prevent free flow at effective velocity in response to steam release. A feature of the invention is this concept that steam traps may be omitted from the main circulating channels provided that steam is released in suflicient quantity to result in such velocity of flow as to sweep the condensate effectively through themain channels of circulation. The elimination of traps reduces the cost of a steam system and also reduces the servicing expense.

Operation with intermittent release of steam the numerous factors that determine the character of intermittent operation. The governing factors of intermittency within the system apart from the washer include: the rate at which replenishing water flows into the tank 23 when reaeoaaoe quired; the extent to which heat loss from the environment from the thermostatic bulb is fa vored; the temperature setting of the thermostat; the degree to which, the arrangement favors lowering the temperature of the thermostat bulb by the flow of replenishing water into the tank 23; the extent to which the introduction of steam into the tank 23 favors raising the temperature of the thermostat bulbythe sensitivity with which the water valve 68 and, the steam valve 12 respond to lowering of the liquid level in the tank 25; and the sensitivity with which the feed pump 86 responds to lowering of the liquid level in-the boiler 20.

In some installations and under some operating conditions We may favor a relatively slow tempo of intermittency or relatively long periods of relatively static conditions. In general, however, we favor seeking high frequency in the intermittent action and relatively high short periods in which the steam releasing valves are closed. Relatively high frequency in the-intermittent release of steam may be sought by various expedientssuggested by the above list of governing factors. now be mentioned.

Rapid inflow for replenishment of the tank 23 may be favored by adjustment of the water valves involved. The tank 23 is of course exposed to the atmosphere and the resulting loss of heat to the atmosphere; together with the flow of replenishing water, causes relatively frequent operation of the valve 65. We have already stated that the thermostatic valveis highly sensitive, the sensitivity being within 1 F. and favoring frequentvalve operation.

With reference-to favoring the effect of newly added water on the thermostat bulb66, it will be noted, first, that th thermostat bulb is at a relatively low level since the relatively cool water in the present temperature range tends to gravitate downward and, second, that the bulb is immediately under the-discharge valve that discharges the cool water into the tank 23.

As for favoring thermostatic response to the introduction of steam into'the tank 23, it is important to note that the thermostat bulb 66 is directly above one of the steam nozzles 63 to lie in the path of bubbles streaming upward from the steam nozzle. Steam discharged from the steam nozzle axially thereof impinges against the adjacent wall of the tank to favor the setting up of an eddy of steam-laden currents of hot water across the thermostat bulb. When the water body in the tank 23 is at a relatively low temperature, the condensing effect of the water on the released steam will tend to keep the thermostat from closing the steam valve. The condensing effect is especially pronounced when new water is being discharged into the tank. The movement of new. water into the region of the thermostat bulb counter tothe upward, move- .ment of steam bubbles is favored. by the higher specific gravity of the relativelycool water, by the downwardly directed kinetic energy ofthe newly added cool water, and by the location of the discharge valve 55 directly above the thermostatjbulb.

It is readily apparent that the location of the thermostat bulb 66 relative to the steam nozzle immediately below is such as to favor prompt closing of the steam valve when replenishing water flow into the tank 23- is cut off. The temperature adjustment of the thermostat and the position of the thermostat relative to the steam Several of these expedients will nozzle below may be such that steam will continue to be released as long as new water is being added and/or as long as the tank water is below the temperature setting. At some temperature settings of the thermostat and within some limits of temperature of the tank water, the tank water in the absence of steam will tend to cool the thermostat below its temperature setting thereby to initiate steam release whereupon the steam bubbles immediately tend to heat the thermostat for closing of the steam valve, the resultant frequency of intermittent action being desirable.

It will be obvious to those skilled in the art that suitable baflles or wall elements may be arranged inside the tank 23 to favor the effect of replenishing flow and/or the effect of steam flow on the thermostat bulb.

Since, as explained, the thermostatic steam valve 65 tends to open and close in response to the starting and stopping of water flow into the tank 23 and since in the specific practice of the invention here under discussion the water valves are adjusted for rapid replenishing flow, steam release by the thermostatic valve 65 tends to ocour in response to the boiler feeding operation. In other words, when a drop in the level of the boiler Water results in operation of the boiler feed pump, withdrawal of water from the lower tank 25 causes withdrawal from the upper tank 23 with consequent initiation of steam release by the valve 65. Obviously a shorter sequence of causes results in opening of the lower steam valve 12 also in response to operation of the feed water pump. Since the frequency with which both steam valves 65 and 12 open under a given heat load on the system depends both upon the responsiveness of the valves 68 and 12 to drop in liquid level in the tank 25 and upon the responsiveness of the feed water pump to drop in liquid level in the boiler 20, we may give special attention to the factors involved in such responsiveness in adjusting our system for intermittent action at relatively high frequency.

In attaining highly frequent. intermittent action we may substitute electrically actuated valves responsive to changes in level in tank 25 or responsive to the automatic Water level switch 90. In the latter arrangement the automatic switch will be sufiiciently sensitive to drop in level in the boiler to cause frequent operation of the feed water pump 88 as well as frequent operation of the two valves 68 and 12.

For a complete understanding of our invention as adjusted for intermittent action at relatively high frequency, it is necessary to give some consideration to the aspect of inherent instability, the tendency of the system to behave as if it were inherently oscillatory.

When the system is adjusted for high frequency operation, it acts as if it were continually hunting or overshooting in restoring some state of balance or-equilibrium. Thus a feature of our invention is the concept of designing a system to hunt" at some desired tempo as a method of attaining intermittent action at that tempo. The high temperature setting of the thermostat is per se a cause of inherent instability since the setting is higher than the temperature of the environment around the feed water supply and can be sustained only by periodic release of steam. Another cause of inherent instability appears to arise from effects appearing alternately at the opposite ends of the system. Thus, condensation of steam or the release of steam towards one end of the system causes flow of steam thereto which flow in turn creates a corresponding demand for additional water by the boiler at the other end of the system. The feeding of additional water to the boiler, however, involves the release of steam to again create demand at said one end of the system.

Upon closer analysis, it is found that the intermittent operation of the system, especially at high frequency, involves a chain of causes as follows: condensation in the system causes a drop in boiler pressure with a consequent tendency for the boiler to form more steam for replacement; the drop in liquid level in the boiler calls for or actually causes approximately a corresponding amount of water to be delivered from the tank .25 to the boiler; the resultant drop in liquid level in the tank 25 causes two actions, namely, momentary opening of the steam valve 12 and replenishing flow of water into the tank 23; the replenishing flow into the tank 23 causes responsive opening of the steam valve 65; the bleeding of steam from the system by the valves 65 and 12 causes a drop in pressure on the return side of the system to tend to bring about repetition of the chain of causes. In other words. there exists what may be called a closed chain of causes which, once set in operation. has a certain tendency to repeat itself regardless of the effect of loss of heat from the environment of the thermostat bulb.

In this ap roach to the invent on. then. we find inherent intermittency of operation arising both from the thermostat setting and the closed chain of causes and u on such inherent intermittent action is imposed the demand of heat from the system, the demand or load desirably modifying the ntermittent action for automatic regulation of the system.

Certain lag factors of importance are found in the system since appreciable time is required for the re ease of a ouantity of steam to cause corres ondin drop in bo ler water level and since appreciab e time is reou red for the drop in boiler water level to cause the addition of new water to the tank 23 and such addition in turn to cause the thermostat bulb 66 to be affected. Because of such lagging factors, when one cycle of causes is closed, lagging forces set in motion during the cycle are effective to tend to repeat the cycle. Because of inherent lag, moreover, steam released may be periodically cut off briefly without causing complete cessation of flow in the system.

A maximum of fourteen per cent of exhaust steam is required to heat feed Water to 212 F., the amount being lower when condensate also is used. Since usually more than this relative amount of steam must be bled off to attain the required velocity Within the system, economy in the use of the released steam is important. Utilizing the released steam to meet an outside hot water demand seldom solves the problem completely because of variations in the outside de-' mand and because of possible long periods of no outside demands.

Releasing steam intermittently is desirable not only because of the dynamic jarring and sweeping action on condensate, but also because of the economy in periodically cutting off stem release.

In some installations intermittent operation may be a desirable compromise between, on the one hand, conserving steam at too great cost in lowering of temperature of the heat exchange surfaces and, on the other hand, bleeding steam continuously to maintain effective velocity in the sys tem at too great fuel cost. In explanation, let it be assumed that the efficiency of the heat exchangers in the system are considered as one hundred per cent in the absence of films of condensate on the heat exchange walls but dropping to only fifty per cent in the presence of films of given thickness. Let it be assumed further that a given high velocity of steam flow will substantially remove such condensate film in :1: seconds and that after cessation of flow the film will be restored progressively over a like period of :1: seconds.

If steam is released for :0 seconds and is then cut off for 2w seconds with efficiency at fifty per cent at the beginning of each cycle, the average efficiency of the system will be 66 (an average of 75% for 1' seconds, an average of 75% for the next period for in seconds, and 50% efficiency for the third period of :r seconds). If a: seconds of steam release alternates with .1: seconds of no steam release, the average efficiency will rise to 75%. If the intermittent action consists of 23: seconds of steam release alternating with x seconds of no steam release, efiiciency will climb to 83 /3%. Each of these successive levels of efficiency involves Stepping up the volume of steam bled from the sytem and an optimum ratio or at least a compromise ratio between the periods of steam release and no release may be found somewhere in such a progressive series. In practice, a desirable mode of intermittent operation may be found in tabulating the fuel costs, labor costs and production for the different modes of operation in the progressive series, the increased production and resulting drop in labor cost per unit of production being weighed against the increase in fuel cost with increase in the proportion of steam bled from the system.

The invention embodied as a sub-combination for adaptation to conventional systems The three tanks 22, 23 and 25 with associated control elements including the thermostatic steam valve 65, the water valve 68, the steam valve 72, and other valves, constitute a sub-combination that .ma be manufactured as an assembly or unit for addition to existing conventional steam systems to convert such systems to the mode of operation contemplated by our invention. While in the described form of our invention the means for providing heated deaerated feed water involves the use of three separate tanks and the use of two separate valves for releasing steam from the system, it will be readily apparent to those skilled in the art that this sub-combination may be simplified and embodied in other forms.

When such a sub-combination is added to a conventional steam plant of the type widely used in .laundry and drying fields, production may be increased fifty to seventy-five per cent. For example, it has been commercially demonstrated that av clothes mangle ordinarily capable of drying fabric at a maximum speed at forty feet per minutes will efiiciently dry the same material at a speed of seventy feet per minute after the present sub-combination is added to the system.

The described adjustments incorporated in the sub-combination result in such flexibility that a given embodiment of the sub-combination may be adapted to the needs of existing steam systems varying over a wide range of capacities and characteristics. When. such a sub-combination is added to an existing installation, the required adjustments to cause the desired mode of operation onthe part of the system may be readily found empiricall in a short period of time without requiring any great skill. If the sub-combination is designed for intermittent action as distinguished from continuous and substantially constant steam release, it will be found that the tempo of the intermittency will rise with increase in the temperature setting of the thermostat. Usually adjustment of the thermostat is all that is required to tune the system, i. e., to arrive at the desired frequency of intermittency. If necessary, attention may be given to other elements in the sub-combination with special attention to sensitivity, as anyone skilled in the art will readily understand upon reviewing the factors in intermittent action heretofore listed.

Other embodiments of the invention In the various forms of our invention now to be described, it will be understood that the steamrelease valves employed may be adjusted either for pulsating continuous release of steam, or for pulsating intermittent release of steam, i. e., may operate either merely to reduce steam release or to stop steam release entirely. It will also be understood that the released steam may be used to heat the feed Water or may be disposed of in some other manner.

In the first described form of our invention, steam is released from the system in accord with demand and demand is measured by the rate at which feed water is required by the system. Another manner in which the release of steam may be related to demand is indicated in Fig. 5.

Fig. 5 shows, byway of example, a heat exchanger in the form of a steam chest I having a heat transfer wall IIII. Steam is conducted from the stem chest through a pipe I82 to a valve I03 for releasing steam at a sufficient rate to result in the required velocity .of flow. In intimate contact with the heat transfer wall IIlI is the thermostat bulb I04 of the illustrated electric arrangement for thermostatically controlling the valve I03 in response to changes in temperature of the wall. As the temperature of the wall IBI tends to drop in response to increased condensation of steam with increased heat demand, the valve I03 tends to open for greater velocity of flow in response to the increase in demand.

Another method of functionally relating the actuation of a system-release valve with the heat load on the system is to vary the fuel feed automatically as required to maintain a given boiler pressure and to vary the release of steam from the system simultaneously with the automatic variation in fuel feed. In Fig. 6 illustrating this conception, a casing I of a familiar type encloses a diaphragm I06, the underside of which is exposed to boiler pressure communicated through the pipe I II! and the upper side of which presses against a plunger I08 that opposes the boiler pressure. The magnitude of the opposing force is determined by the adjustment of a weight III] slidably on a lever III. The lever III which is fulcrumed on a suitable bracket H2 and is connected to the plunger by a link I I3 carries at its outer end a switch contact IIS intermediate two spaced switch contacts IIS and III. When pressure in the boiler of the steam system drops below a value predetermined by the setting of the weight III), the contact II5 drops against the contact I I I to close the following circuit for energizing a motor H8 in one direction: contact II5, contact III, wire I20, field winding I2I, the armature of the motor, wire I22, battery I23, and wire I back to the contact II5. On

the other hand, when the boiler pressure rises above the predetermined value, contact II5 touches contact IIB to close the following circuit for reverse rotation of the motor I I8: contact I I5, Wire I26, the reverse field winding I22, the armature of the motor, wire I22, battery I23, and wire I25 back to the contact I I5.

It is apparent that by virtue of this automatic control through a reversible motor, a worm shaft I28 operated by the motor will seek a position of rotation in accord with the load or heat demand on the system. One worm I38 on the shaft I28 controls a worm gear I3I for valve regulation of flow through a fuel pipe I32 to the burner for the boiler, and a second worm I33 on the shaft controls a worm gear I35 that operates a valve I35 (Fig. 7) for releasing steam from the system through a pipe I 31. The pipe I3! may lead to a feed water supply to transfer heat thereto or may simply release steam into the atmosphere.

In the arrangement shown diagrammatically in Fig. 8, the rate of steam release from the system varies with the load or demand on the system as measured at a number of points along the system. In Fig. 8 a boiler I supplies live steam through a pipe MI to four different heat exchangers I42, steam passing from the four steam exchangers through four pipes I 43 respectively to a low pressure pipe I55 on the return side of the system. The pipe I45 communicates with an exhaust pipe I48, the function of the exhaust pipe being to release sufficient steam from the system to maintain the velocity of flow required for productive efficiency.

Each of the pipes I43 is provided with an electrically actuated valve I46 each of which valves is responsive to the temperature changes of the corresponding heat exchanger I42. To provide for such response, each of the four valves I 26 is operatively connected by a multiple conductor cable I41 with a corresponding thermostat control I48 at the correspondingheat exchanger I42, each of the thermostats controlled including a thermostat bulb I50 lying against the heat-transfer wall of the heat exchanger.

When the heat demand imposed on any one of the heat exchangers I42 is relatively low, the corresponding valve I tfi will be automatically adjusted to a relatively low rate of steam flow through the heat exchanger suflicient to main tain the heat exchanger Wall at the temperature predetermined by the setting of the thermostat. Whenever an increase in the demand for heat tends to lower the temperature of the heat exchange wall, the corresponding valve I46 will automatically operate to increase the rate of steam flow through the heat exchanger to meet the increased demand.

The first described form of our invention as illustrated in Figs. 1-4 may be analyzed as employing the feed water supply simply as thermal means for controlling intermittent action in response to demand, the thermal means being heated in response to release of steam and being thereby maintained at an artificial temperature sufiiciently high for the particular system. The same principle of operation will be recognized in the electrical arrangement shown in Fig. 9. In Fig. 9 an ordinary alternating current circuit includes in series a solenoid I54 for operating a steam-release valve I55 and a relay I56 for controlling the solenoid. When the solenoid is deenergized, a spring I51 moves the valve towards closed position. The coil I58 of the relay I56 is in a control circuit energized by a transformer ree. The contr'olcircuit includes 'insiies the 'relay-{coilf'ltd the secondary of the transformer I'6 E3, a--heatingcoil Ifil for heatinga thermostat ,means such as a bimetallic element I62, a contact -I-$-3 movable by the thermostat means, a

"complementary stationary contact I65, and arheiostat i'fit'for adjusting current flow through the circuit. I v

The control arrangement in Fig. 9, as described 3m this p t, may be employed for intermittent steam release independently of variationsin demand, that is to say, for a substantially constant level of intermittent steam release highenough to meet peakdemands on the'system. When the thermostat means I62 cools suiiiciently to close the control circuit, the resultant current flow "through the circuit energizes the heating coil IIiI toinitiate-a heating period for again causing separation of the contacts I63and I 55. It is apparent that the circuit will open and closefor jnelmittent current flow with the alternating periods'determined by the design of the thermostat means, the design of the heating coil, the

current in the circuit, and'the adjustment of the rheo'stat I66. In' 'a control circuit of a given design, the character of the intermittent action be va'riedsimply by adjustment of the rhe- -'ostat.

{To introduce the factor of demand where variation in steam-release in accord with variation in heatdemand is desired,'we may add to the control circuit in' Fig. 9a shunt I51 controlled by a shunt switch lee, such that closing ofthe shunt switch fwillenergize the coil I58 of the relay independently of control bythe thermostat means I52. The shunt switch IE8 maybe operatively connected to the'steam system in various "ways to respond to changes in the load. For exam le, the shuntswitch I68 may be caused to close in response" to operation of the feed pump "se r response to the changes in waterlev'el in 25 that cause opening of the water valve Fig. 10 illustrates the fact that under our-basic concepts timing devices of other than the ther- L mal'type may be employed in some practices of our invention. Fig. 10 shows an electric clock or constant-speed motor E16 in parallel with the prin laryof'a'transformer I1I and'in parallel with an actuating'oircuit. The actuating'circuit has in'seri'es a solenoid I12 to actuate a steam release valve" 'l'lfi'a'nd arelay I15 to control the solenoid.

The coil Ht of therelay is in a control circuit that isenergizedby the transformer HI and is intermittently opened and closedby a switch means I11.

the constructionshown in the drawings, the 'ch-me'ans It? comprises a pair'of stationary cts and a rotary switch member, the rotary 1' member being keyed to a square shaft I18. I inglydnounted' on the'square shaft I18'for ac ation thereof is a sleeve I88 integral with a notion wheel IiiL'the sleeve being controlled by position onthe friction wh'el lillwith respect-to 18 the driving-disc I81 asset'by manipulation of the thumbpiece I 86 will determine the rate at which the switch means "I11 will intermittently close and open the operating circuit.

The arrangement illustrated in'Fig. 10 asdescribed to this point may be employed to' cause intermittent release of the steam independently 'of'variations in demand, the rate of steam re- "lease being high enough to satisfy peak loads on the system. To introduce demand as a factor, it is merely necessary to add a shunt I83 controlled by a shunt switch I90 and to arrange for'the shunt switch to close automatically whenever the 'feed pump'operates to replenish the boiler water.

Fig. l1,'which is similar to Fig. 10 in many "detailsas indicated by the use of corresponding numerals for corresponding parts, illustrates how the factor of "demand may vary adjustment of thenut I83 rather than shunt the control circuit. Fig. 11 differs from'Fig. 10 in having the worm I integral with a shaft I9! driven by a reversible motor I922. The motor I92 is reversibly controlled in thesame'manner as the motor I I8 inFig. 6; th'us'Fig 11 showsthe same reversing circuits as Fig. 6 including the two oppositely wound field windings I2I and I21, wire "I22; battery I23, wire I25,"the two fixed contacts "H6 and H1, and the intermediate contact H5 carried by the pressure respon'sive lever I I I.

Rotation of the worm shaft I9I in response to demand not only'shifts the "position of the nut I83 tovary' the rate of intermittent steam re- "le'ase but alsoxchanges the rotary position of a 'worm' gear I93 for-valve control of fuel through a pipe I95, thefuel rate being increasedand decreased as required to maintain a predetermined boiler pressure. Thus, when demand or the heat load on the system increases, thefriction wheel "I8I -in-Fig. 11 is moved radially outward with respect to the drive disc I81 to increase the fre- -quency with which the switch means I11 intermittently closes the' control switch for actuation 'of thestea'm release valve. If desired, a suitable dash pot I89 may be operatively connected with the valve I13 tohave retarding effect only "on the valve-closing movement, the retarding *effect being variablebyadjustment of a needle valve 1 94 as shown.

Fig. 12 shows another electrical arrangement for intermittent release of steam from asystem "as required for the creation of effective-steam flow. The usual circuit for energizinga solenoid 1-96 for actuation of a steam-"releasevalve I91 is controlled by a relay 198. 'The coil 200 of the relay is 'en'ergized'and controlled by an electric or electronic timer 202. The timer 202 is of-a familiar type including a battery or'other F. "source, a condenser and suitable resistance, the timing function being provided by the'charging or'discharging of the condenser. Since such "timers are well known in the art, it is not deemed necessary to make a detailed disclosure of'its construction. With the periodic riseand decay of current incidental to the charging and discharging of the timer condenser, the relay coil is periodically energized to cause periodic operationof the steam va'lve I91.

'For' time adjustment of the periods of relay energization, itis merely necessary to' vary the capacitance-'and/or resistance'in the timer 202. *For'such purpose, the timer isshown in Fig. :12 as having a manual condenser adjustment 293 and a manual resistance-adjustment or rheostat knob 265. 'If itis desirable to'introduce demand on the steam system as a factoryit ism'e'rely 19 necessary to provide a shunt 208 controlled by a shunt switch 201, the switch closing in response to replenishment of the boiler or replenishment of the feed water supply.

Fig. 13 indicates how demand may be introduced as a factor to vary the adjustment of a timer rather than to shunt the timer. The valve l9! in Fig. 13 responds to the same actuating circuit as in Fig. 12, the circuit including the solenoid I96 and being controlled by the same relay I98. The coil 200 of the relay is controlled and energized by an electric timer 2i0 of the same type as the electric timer 202 but having only a single timing adjustment in the form of a worm gear 2. the switch 201 of Fig. 12 is shown in Fig. 13, but such a switch may be added if it is desired to have the release of steam from the system augmented by means responsive to replenishment of the boiler or of the feed water supply. A shaft 2|2 operated by a reversible motor 2 l3 carries a worm 2i5 in mesh with a timing worm gear 2 and also carries a second worm 2H5 in mesh with a second worm gear 2 I! for valve regulat on of fuel flow through a fuel pipe 2 l 8. motor 2| 3 is controlled in response to demand on the steam system by the previously described reversing circuits as indicated by the use of numerals for motor circuit elements in Fig. 13 corresponding to numerals in Figs. 6 and 11.

When, in the operation of the apparatus illustrated in Fig. 13, pressure in the boiler of the system drops below a predetermined value the contact H on the boiler-pressure-responsive lever Ill drops against the contact H1 to close the motor circuit through the field Winding I21 for energizing the motor 2| 3 in one direct on. On the other hand. when the boiler pressure rises above a predetermined value contact H5 on the lever Iii touches contact H6 to close a circuit through the reverse field winding 12! to energize the motor 2l3 in the opposite direction.

It is apparent that by virtue of this automatic control through a reversible motor the worm shaft 2 l2 operated by the motor will seek a position of rotation in accord with the load or heat demand on the system. When the demand is high the worm gear 2", controlled by the worm 216, will cause the fuel valve to supply fuel to the boiler at a relatively high rate, and the worm gear 2| I, controlled by the worm 2l5, will cause the timer 2H) to be adjusted for intermittently opening the valve I91 to release a relatively great quantity of steam in a unit of heat.

Fig. 14 illustrates an arrangement for intermittent steam release in which the frequency of the intermittency is constant but the intervals of relatively great steam release are varied in length in accord with heat demand. A valve 220 for controlling the release of steam from a heat exchanger 22! is operated by a solenoid 222 in series with a relay 223. The coil of the relay 223 is connected to a brush 225 mounted on a carriage 225 and is in series with a transformer 22'! and a second brush 228. The first brush 225 presses against the face of a rotating disc 230 of non-conducting material and the second brush 228 presses against a metal band 23l around the periphery of the disc. For intermittently closing the relay coil circuit the metal band 23l is in turn connected to a plate 232 of conducting material covering a portion of the surface of the disc 230.

The carriage 226 which slidingly engages a guide rod 233, is controlled by a worm 235 and No switch corresponding to The battery 256.

20 is adapted for moving the brush 225 along a: radius of the disc 23!]. The shape of the plate 232 is such that the proportion of a rotation of? the disc during which the brush 225 is in contact with the plate 232 depends upon the radial position of the brush. Thus, when the brush is: positioned near the axis of the disc the relay 223 will be energized substantially continuously but; at positions of the brush away from the axis, the: relay will be energized periodically, the duration. of the energization periods decreasing with the. radial distance. The frequency of the intermittent relay action is constant since the disc 230; is driven by a clock or constant speed motor 235..

A motor 231 for controlling the worm 235 is. reversibly controlled by circuits of the character previously described, energization of the motor being determined by the position of a switch arm 238 and the position of the switch arm 238; being in turn determined by the surface temperature of the heat exchanger 22]. In Fig. 14'- the switch arm 238 is operated by a thermostat arrangement including a thermotat bulb 240 in contact with the heat exchanger 22i. At a pre determined surface temperature of the heat exchanger the switch arm 238 is in the central position shown: at higher temperatures, the: switch arm is swung to one limit position to shift the brush 225 radially outwardly along the disc 230; and at lower temperatures the switch arm is swung to the opposite limit position to shift. the brush 225 radially inward. It is apparent that the position of the brush radially of the disc: and therefore the rate of steam release will vary with the heat load imposed on the heat exchanger 22i.

Fig. 15 illustrates another arrangement for obtaining intermittent steam release. The solenoid 24l for operating the steam release valve 242 is controlled by a relay 243. The circuit for closing the relay 243 is adapted by any suitable mechanical or electrical arrangement to close whenever replenishing water is periodically added to the boiler or whenever replenishing water is periodically added to the feed water supply. For example, the relay circuit may in turn be controlled by a normally closed back con-- tact relay 245, the coil of which is energized by the motor circuit of the feed water pump 86. The described arrangement magnetically holds the release valve 242 at its maximum open povsition whenever the feed water pump is idle,

but releases the valve to reduce or cut off steam flow whenever and as long as the feed water pump is energized. The arrangement therefore is inherently intermittent in operation.

The arrangement shown in Fig. 16 provides for periodic release of steam in lagging response to periodic boiler feed operation and further provides for variation in the duration of the responsive steam release. A relay 246 shown in its de-energized position in Fig. 16 incorporates three switches, namely, a normally closed switch 241, a normally open switch 248, and a normally closed switch 249. A solenoid 250 for operating a steam release valve 25! is in the plate circuit of a vacuum tube 252, the plate circuit being energized by a battery 253 or other electromotive source and including the normally closed switch 249.

The grid of the vacuum tube 252 is connected to one side of a condenser 255, preferably a variable condenser as shown, and the other side of the condenser is connected to a grid-washing A circuit for charging the condenser: 255:1s: provided by avbattery 251' miseries .withthe normally open switch 248 and. a; conducting path' for discharging the. condenser. is provided by. a variable resistance 269' in series with the normally closed switch 241..

Normally, with the boiler feed. pump de-energized" and the relay 246 in theposition shown, the plate circuit of the vacuum tubeis closed but the solenoid 250' is not energized to hold the steam. valve 25! in a maximum. open position: because the normal negative bias given to the grid of the tubeby thebattery 256 prevents current iiow through the plate circuit. Normally the condenser 255 is completely disch-argedsince the charging circuit is held'open by the switch 248 and the discharging circuit is closed bythe' switch 241.

When the feed water pump is periodicallyenergized, relay 246 is likewiseenergized to open switches 24Tand 249' and close switch 248 thereby causingthe battery 25'! to charge the condenser 255. Immediately the-grid of the vacuum tube becomes positive but the switch 249 is open to prevent current flow through the plate circuit. When the feed water pump ceases to opperate, relay 246 returns to its normalposition whereupon the valve 25I'is open to its maximum position and stays open substantially as long as the grid potential is positivein response to discharge of the condenser through theresistance 250. When the condenser is completely dis charged, the battery 256 assumes its normal negative control of the gridpotential to (lo-energize the solenoid 250.

It is apparent that the condenser 255 and the resistance 2613 provide a timing circuit in which the duration of the condenser discharge maybe controlled by adjustment of the resistance and/or adjustment of the condenser. Only ordinary skill is required to adjust the duration of the responsive delayed-action steam release to cause the steam heating system to operate efficiently. The rate and duration of the delayed'steam release to be soughtissuch as will cause the cycle of operation to be repeated often enough for effective removal of condensate from the system.

We have disclosed'various expedients'for cans-'- ingvelocity in the system to vary with the volume of'feed water utilized, one expedient involving the-use of a thermal-responsivemeans, another the use of a liquid-level-responsive means. Other expedients are suggested by our disclosures. In Fig. 2, for example, the rateat which steam cond nses in the submerged portion of'pipe 34 varies inversely asthe temperature of the water and such condensing action as affected by the'addition of relatively cool water to the supply may be'utilized to afiect the ve' locity of steam flow in the system;

It-should be understood that in the claims'the use of the expression continual flow or the expression substantially continual flow should" sters new International dictionary, the first" meaning being occurrence without interruption and the second meaning being occurrence at'fre quent intervals. Thus, under eithermeaningot the term a steam condition. prevailsthatprovides 22 suflicientlycontinuous'pressure' and movement to effectively removenon-condensabl'e gases and water from 'the condensing surfaces of the steam apparatus and: to maintain the surfaces substantially fre'e'fiom non-ccndensahle gases and anyWate-r film o'f mater ial thickness whereby additional heat units reach such surfaces to increase therate or heat transfer. Any steam condition, pressure, or flow that accomplishes this end should be construed to be within the terms and meaning of continual flow of steam.

Through the specification, wehave emphasized the impor tance'of maintaining the interior surfaces of thehea't exchange surfaces substantially free oficondensation in order to obtain maximum heat transferb'etwe'en the steam the heat exchanger wall; We wish to make clear, however, that this doesnot mean that the interior surfaces "of the heat exchanger are maintained in an absolutely dry condition but rather that the thicknessof the-film of condensate is held to such limits that the desirable results may be obtained; We have found that an interior heat exchange wall, which is merely moist as distinguishedifromone having a substantial layer of condensate thereovendoes not impair the heat transfer characteristics of our system and may even assist in obtaining the desired results. Hence, .inthe appended claims, statements to the effect" that" condensate is to be removed from the walls do not exclude moist walls. In fact, moistiwalls necessarily result from the passage of saturated steam even'at exceedingly high velocities:-

It'Should be understood that throughout the specification and the-appended claims, the expressions intermittent release of steam and operationwithintermittent release of steam and thelike are intended to denote the release of steam: at a varying rate, which may vary fromsome-positive value to zero, or from some positive value to a lower value, such as the case when the valve'doesnot completely close or because a bypass is provided. ihis is not to be confused with the definition heretofore given for pulsating intermittent flow of steam in which it is-contemplated that there will be complete cessation of steam flow between pulsations, in contra-distinction to pulsating continuous flow of steam inwhich-the rate of steam flow varies between different positive values.

Thexvarious practices and forms or our invention set forth in detail herein will suggest to those skilled'in the art various changes a d sub stitutions based on ourunderh' ing ccncepts. We reserve the right to all such departures from our description that properly lie within the scope of our: appended :claims;

Weclaim:

1; In a steam system, a heat exchanger, a boiler connected w'ith said heat exchanger to supply steam I thereto; means to release steam from the system on the low pressure side oi said exchanger, andmeans-respon'sive to the boiler pressure to vary the rate of 1 fuel consumption by the boiler inverselywith changes in'the boiler pressure and to vary' the rate of steam release in accord with the rate of fuel consumption.

2. Ina-steam system, a' heat exchanger, a steam generator connected with said heat exchanger to supply st'eamthereto, variable fuel feeding means for'said generator inversely responsive to steam pressure at the'boilerto maintain steam pressure at the 'boiler at diiferent levels of demand, and means3responsivetosaid fuel feeding means to release steam from the system on the low pressure side of said heat exchanger at a rate varyin with the heat demand on the system.

3. A heat exchange system comprising a steam using device for heating primarily by the release of latent heat with consequent formation of condensate, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust steam pipe in open communication with said steam generator through said device, a valve controlling the release of steam from said exhaust pipe into a pressure much lower than that maintained within the system by the generator, timing means operatively connected with said valve to operate the valve intermittently to cause pulsating flow through said device, and means apart from the system to energize said timing means.

4. A heat exchange system comprising a steam using device for heating primarily by the release of latent heat with consequent formation of condensate, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust steam pipe in open communication with said steam generator through said device, a valve controlling the release of steam from said exhaust pipe into a pressure much lower than that maintained within the system by the generator, and electrically actuated timing means operatively connected with said valve to operate the valve intermittently to cause pulsating steam flow through said device.

5. A heat exchange system comprising a steam using device, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust pipe in open communication with said steam generator through said device, means to release steam from said exhaust pipe into a pressure much lower than that maintained within the system by said generator, an electrically actuated timing means to operate said release means intermittently to cause pulsating steam flow through said device, means to supply water to said steam generator as required, and means to operate said release means in response to operation of said water supply means.

6. A heat exchange system comprising a steam using device, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust pipe in open communication with said steam generator through said device, means to release steam from said exhaust pipe into a pressure much lower than that maintained within the system by said generator, an electrically actuated timing means to operate said release means intermittently to cause pulsating steam flow through said device, means to supply water to said steam generator as required, means to operate said release means in response to operation of said water supply means, and means to vary the operation of said timing means to meet various levels of heat demand on the system.

7. A heat exchange system comprising a steam using device, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust pipe in open communication with said steam generator through said device, means to release steam from said exhaust pipe into a pressure much lower than that maintained within the system by said generator, an electrically actuated timing means to operate said release means intermittently to cause pulsating steam flow through said device, means to supply water to said steam generator as required,

24 means to operate said release means in response to operation of said water supply means. and automatic means to vary the operation of said timing means in response to changes in the heat load on said device.

8. A heat exchange system comprising a steam using device, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust pipe in open communication with said steam generator through said device, means to release steam from said exhaust pipe into a pressure much lower than that maintained within the system by said generator, an electrically actuated timing means to operate said release means intermittently to cause pulsating steam flow through said device, means to supply water to said steam generator as required, means to operate said release means independently of said timing means in response to operation of said water supply means, and means to vary the frequency at which said timing means operates to meet various levels of heat demand on said device.

9. A heat exchange system comprising a steam using device, a steam generator connected to said device for supplying steam thereto at relatively high pressure, an exhaust pipe in open communication with said steam generator through said device, means to release steam from said exhaust pipe into a pressure much lower than that maintained within the system by said generator, an electrically actuated timing means to operate said release means intermittently to cause pulsating steam flow through said device, means to supply water to said steam generator as required, means to operate said release means independently of said timing means in response to operation of said water supply means, and means operatively connected to said timing means to vary the duration of the steam release to meet various levels of heat demand on said device.

10. In a heat exchange system comprising a steam using device for heating primarily by the release of latent heat with consequent formation of condensate, a steam generator connected to said device for supplying steam thereto at relatively high pressure, means to release steam from said system on the low pressure side of said steam using device to promote steam flow through the system, timing means including a continuously driven timing switch, and means to operate said release means intermittently in response to said timing means.

11. In a heat exchange system comprising a steam using device, a steam generator connected to said device for supplying steam thereto at relatively high pressure, means to release steam from said system on the low pressure side of said steam using device to promote steam flow through the system, a timing means operatively connected with said release means to release steam from the system intermittently, means responsive to variations in the steam pressure at said steam generator to vary the rate of fuel consumption by the steam generator thereby to minimize the changes in steam pressure with changes in heat demand on the system, and means responsive to said fuelconsumption-varying means to vary the operation of said timing means thereby to vary the release of steam in accord with changes in the heat demand on the system.

-12. In a heat exchange system comprising a steam using device for heating primarily by the release of latent heat with consequent formation of condensate, a steam generator connected to said device for supplying steam thereto at relatively high pressure, means to release steam from said system on the low pressure side of said steam using device to promote steam flow through the system, a timing means operatively connected with said release means to release steam from the system intermittently, and means including a thermostat responsive to temperature changes of said steam using device to vary the operation of said timing means and thereby vary the rate of steam release in accord with changes of heat demand on said device.

13. In a heat exchange system comprising a steam using device for heating primarily by the release of latent heat with consequent formation of condensate, a steam generator connected to said device for supplying steam thereto at relatively high pressure, means to release steam from said system on the low pressure side of said steam using device to promote steam flow through the system, a timing means operatively connected with said release means to release steam from the system intermittently, and means including a thermostat responsive to temperature changes of said steam using device to vary the frequency of operation of said timing means in accord with changes of the heat load on said steam consuming device.

14. In a heat exchange system comprising a steam using device for heating primarily by the release of latent heat with consequent formation of condensate, a steam generator connected to said device for supplying steam thereto at relatively high pressure, means to release steam from said system on the low pressure side of said steam using device to promote steam flow through the system, a timing means operatively connected with said release means to release steam from the system intermittently, and automatic adjustment means for said timing means to vary the duration of the recurring periods of steam release, said adjustment means including a thermostat responsive to temperature changes of said steam consuming device thereby to vary the steam release in accord with changes in demand on said device.

ELMER PAUL HARRISON.

ORVILLE A. HUNT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,399,052 Ellis Dec. 6, 1921 1,618,177 Ellis Feb. 22, 1927 1,812,897 Owens July 7, 1931 2,311,236 Kucera Feb. 16, 1943 2,366,332 Harrison Jan. 2, 1945 

